1. Field of the Invention
The present invention relates to a device for peel test used, for example, for testing the adhesive force of adhesive tapes or adhesive sheets, peel strength in the case of two bonded members, and the adhesive force of surface coatings formed by plating or the like.
2. Description of the Related Art
A peel test is a test method conventionally conducted to measure the adhesive force (sticking force) of adhesive tapes or adhesive sheets, and the peel strength of adhesive agents and the like. Examples of the peel test methods include a 90-degree peel test, a 180-degree peel test, a T-peel test, and a peel test with a floating roller. A 90-degree peel test and a 180-degree peel test applied as test methods for adhesive tapes or adhesive sheets are defined, for example, in JIS Z 0237. A 90-degree peel test, a 180-degree peel test, a T-peel test, and a peel test with a floating roller applied as test methods for adhesive agents are defined, for example, in JIS K 6854-1, 6854-2, 6854-3, and 6854-4 respectively.
The 180-degree peel test is largely affected by the strength or the degree of elasticity of a base material if it is applied for measuring an adhesive force such as that of an adhesive tape. Accordingly, the 90-degree peel test is considered as a preferred method of measuring such an adhesive force. However, the 90-degree peel test has found difficulty in maintaining a peel angle (angle formed between a test plate an adhesive tape sticks to and the adhesive tape being pulled) at 90 degrees all the time during the test. To be specific, the 90-degree peel test measures a load acting when a material such as an adhesive tape sticking to a test plate is pulled away from (peeled off) the test plate by pulling one end of the adhesive tape in a direction at an angle of 90 degrees to the test plate. A peel position moves transversely on the test plate as the adhesive tape is pulled away further, resulting in a problem of change of a peel angle.
A technique of transversely sliding a test plate with a dedicated jig for a distance corresponding to the peel length of a material such as an adhesive tape is introduced in JIS Z 0237 (see Non-Patent Literature 1). More specifically, this jig has an upper grip for gripping one end of a material such as an adhesive tape, and a lower grip for gripping a jig with a slidable test plate. The jig is configured such that, as the upper and lower grips are separated further from each other, the test plate is pulled with a string to move slidingly.
A technique that does not involve mechanical interlock of peeling of an adhesive tape and the sliding movement of a test plate is proposed (for example, in Patent Literature 1). This technique makes the sliding movement of a test plate with a material such as an adhesive tape sticking thereto with a stepping motor and a ball screw.
Patent Literature 1: Japanese Patent Application Laid-Open No. 9-113438
Non-Patent Literature 1: Japanese Industrial Standard JIS Z 0237
The technique of sliding a test plate with a string disclosed in Non-Patent Literature 1 mentioned above may generate a difference between a peel length and a sliding distance of the test plate due to flexure or stretch of the string, leading to a problem as a peel angle is changed during a test. In particular, a test plate may slide a distance longer than a peel length due to inertial force, or the test plate may vibrate violently if a peel test is conducted at a high speed. This results in a problem of considerable reduction of measurement accuracy.
The technique disclosed in Patent Literature 1 mentioned above requires driving units for driving a fixing part for fixing (gripping) an end of a material such as an adhesive tape and for driving a test plate, and also requires individual controls of the traveling speeds of the driving units. This results in a problem of the complex and high-cost structure of a measuring device.